Renal System Flashcards
process of evolution in kidneys
- auqatic organisms used cellular transport to miaintain differences between ECF and seawater
- development of out epithelial layer to restrict water flow into body
- terrestrial environment = diversifying limits to water loss
vertebrate renal evolution
- pronephros = single giant nephron does filtration for body, simple blood vessels and cilia on tubules for filtration, k=kidney directly connected to veins, single nephron
- mesonephros = bowmans capsules formed at end of tubules (c shaped cups capsules), 24-100 nephrons, glomeruli present
- Metanephric = ureter emergence, clusers of many smaller nephrons (millions)
loop of henle
- used to concentrate urne
- ascending loop not formed a birth
- ascending and descending limbs
features and functions of kidneys
- villi = increase SA for transport
- mitochondria abundance = energy for active transport
- tight junctions = block passage of solutes between cells -> barrier = control
- transporters = allow movement/transport
- renal tubules are lined with epithelial cells -> used paracellular and transcellular transport
What is transcellular transport
- need proteins on both sides of membrane/cell to move solutes through
what is paracellular transport
- solute moves through junctions between cells
process occuring in kidneys
- filtrattion -> movement of solutes/solvent from blood into kidney (bulk movement from glomerullar capillaries to neohron)
- reabsorption -> movement from filtrate to peritubular capillaries (back into renal vein and blood)
- secretion -> movement of specific solutes from peritubular capillaries back into filtrate
- Excretion -> loss of filtrate as urine intto bladder via ureters
explain the structure of glomerulus
- coarse seive
- capillaries are very leaky between cells (only protein and blood filtered)
- epithelial cells = podocytes
what is GFR
- glomerular filtration rate
- volume of fluid filtered by both kidneys per unit of time
What factors determine GFR
- permeability of filtration barrier
- SA for filtration
- glomerular filtration pressure (only one to change short term)
What two pressure gradients determine filtration across the glomerulus
- hyrdostatic pressure (exerted by fluid inside pressure on walls)
- oncotic pressure (exerted by water moving down conc gradient)
what are the pressure gradient differences across the glomerular capillary and bowman’s capsule?
- hydrostatic pressure higher in glomerulus than bowman’s
- osmotic pressure higher in glomerular capillary due to proteins (no protein in bowman’s capsule)
how does capillary hydrostatic pressure influence GFR
- mean arterial pressure (increased = increased glomerular pressure = increased filtration)
- afferent resistance -> increased resistance = decreased glomerular pressure = lower filtration)
- efferent resistance = high glomerular pressure = higher filtration
what occurs in the proximal tubule?
- bulk reabsorption of nutrients
- unregulated absorption
features of proximal tubule for absorption
- surrounded by dense capillary network
- winding structure (convoluted)
- extensive microvilli,
- high numbers of mito,
- “leaky” tight junctions (lots of stuff leaving tubule between cells),
- many and diverse transporters
What occurs in the descending limb of henle
- passive water reabsorption
- permeable to water, not salt/ solutes
- water moves down electrochemical gradient through aquaporins in descending Limb all the time (always there)
How does ECF concentration determine conc of urine in descending loop
- fluid can only have osmolarity same as ECF because will only flow when there is a concenntration gradient
- must be a difference for water to flow, so once it reaches isotonic level will stop
- further down loop, more concentrated
What occurs in ascending loop of henle?
- active solute reabsorption
- impermeable to water and salt is actively transported
- decreasing concentration on ascension -> removing salt
- transporters moving Na+ and Cl- across into blood, dependent on K+ cycling on both apical and basolateral membranes because sets up conc gradients
What occurs in the Collecting duct?
- regulated water reabsorption
- use of hormones to control transport
- fine tuning of composition of urine in distal tubule
Effects of ADH (antidiuretic hormone
- opposes production of urine (decrease vol), will increase reabsorption of water into blood to reduce filtrate
-passive movement of water turned on and off by hormones moving aquaporins
steps of ADH movement of aquaporins
- ADH acts on basolateral membrane receptors
- triggers exocytosis of aquaporin storage vesicles inside membrane cells of collecting duct
- increases aquaporins in luminal membrane
- increases water reabsorption
How is concentration of urine changing dwn collecting duct if no ADH present?
- it cannot change because water can’t move across the apical/lumen membrane